Intravascular stent

ABSTRACT

An expandable stent for implanting in a body lumen, such as a coronary artery, peripheral artery, or other body lumen. In one aspect, the stent includes a butterfly pattern to which connecting links are attached. In another aspect, the stent embodies a non-directional structure.

BACKGROUND OF THE INVENTION

The invention relates to vascular repair devices and, in particular, tointravascular stents including rings with sub-structure reducing strainand enhancing flexibility as well as to stents having non-directionalstructural patterns.

Stents are generally tubular-shaped devices which function to hold opena segment of a blood vessel. They also are suitable for use to supportand hold back a dissected arterial lining that can occlude the fluidpassageway. That is, whether self-expanding or expandable using force,stents are delivered within vasculature in a radially compressedconfiguration and then implanted at an interventional site whileassuming a radially expanded configuration. At present, there arenumerous commercial stents being marketed throughout the world. Forexample, some known prior art stents have multiplex cylindrical ringsconnected by one or more links. While some of these stents are flexibleand have the appropriate radial rigidity needed to hold open a bloodvessel, there typically is a tradeoff between flexibility and radialstrength and the ability to tightly compress or crimp the stent onto acatheter so that it does not move relatively to the catheter or dislodgeprematurely prior to controlled implantation at an interventional site.

As stated, various conventional stents include a plurality of ringsconnected by links. In certain stents, the rings include a plurality ofpeaks and valleys connected by bar arms. When these rings are positionedin phase relatively to one another, W-crests and Y-crests are formed atthe points of connection between the links and rings. Once a stentembodying this structure is implanted at an interventional site, asignificant amount of strain is placed upon the peaks and valleys. Infact, the link can become angulated or twisted upon stent expansionresulting in an overall twisted stent configuration. Such a twistedstent configuration can suffer from inadequate vessel wall appositionand thus, may not perform optimally in holding a vessel open. Further,the degree of twisting often cannot be predicted due to manufacturingand material variability which consequently limits the reliability ofstent function.

Other factors also contribute to the unpredictability of stentperformance. That is, conventional stents embody a pattern of links andrings which can be characterized as directional in configuration. Atypical stent include a pattern of adjacently arranged rings whichextend the length of a stent and includes a first end which differs fromthat of a second end of the stent. Due to this directional structure,such a stent must be placed upon a catheter in a particular direction sothat when it is deployed and implanted within vasculature, the stentwill be arranged as contemplated to achieve expected performance.Unfortunately, conventional stents embodying directional structure canbe placed on a catheter incorrectly due to operator error, and it isdifficult to either identify this error or correct it during a surgicalprocedure.

Accordingly, what has been needed and heretofore unavailable is a stentincluding structure which provides desired flexibility withoutcompromising radial strength and reduces unwanted stresses and twisting.Moreover, there is a need for a stent which addresses problemsassociated with directional stents. The present invention satisfiesthese and other needs.

SUMMARY OF THE INVENTION

The present invention is directed to an intravascular stent includingstructure enhancing flexibility without compromising radial strength andminimizing twisting and inherent stresses. The present invention is alsodirected towards a stent incorporating a non-directional pattern ofrings and links.

In one aspect, the invention includes a flexible intravascular stent foruse in a body lumen, comprising a plurality of cylindrical rings alignedalong a common longitudinal axis and interconnected to form the stent,each cylindrical ring having a first delivery diameter and a secondlarger implanted diameter. Each cylindrical ring includes an open W orbutterfly pattern to which one end of a link between adjacent rings isconnected. Further, each ring includes a plurality of first peaks,second peaks, and third peaks, adjacent third peaks defining thebutterfly pattern. Each of the peaks has a height and an apex, the firstpeaks being taller than the second peaks, and the second peaks beingtaller than the third peaks. Described in another way, each cylindricalring has a plurality of first valleys, second valleys, and thirdvalleys, adjacent third valleys forming the butterfly pattern. Moreover,each of the valleys has a depth and an apex, the first valleys beingdeeper than the second valleys, and the second valleys being deeper thanthe third valleys.

At least one link attaches each cylindrical ring to an adjacentcylindrical ring. The links can include an undulation having a curvedportion extending transverse to the stent longitudinal axis toward thesecond peak. Additionally, the curved portion of the undulating link canbe longitudinally aligned with the second peak. Also, each undulatinglink can include an arm that is straight and parallel to thelongitudinal axis of the stent and which is circumferentially offsetfrom the second peak.

The invention further contemplates peaks and valleys having a differentradii and/or heights than other or adjacent peaks and valleys. In stillanother aspect of the invention, at least a portion of the links orcylindrical rings can have a variable thickness configuration and/or avariable width.

Still another aspect of the invention is directed towards anon-directional stent. Such a stent is not required to be mounted onto astent delivery system in a particular proximal-distal orientation. Theconfiguration of peaks and valleys at a proximal end of the stent isgenerally a mirror image of the configuration of peaks and valleys atthe distal end. Both the proximal end and the distal end cylindricalrings may include various combinations of tall peaks, intermediatepeaks, short peaks, deep valleys, intermediate valleys, and shallowvalleys. Further, the non-directional stent can include the open W orbutterfly pattern. In one embodiment, at least two of the open W orbutterfly pattern configurations face in opposite directions from eachother along the length of the stent. In addition, it is contemplatedthat not all of the curved portions of the undulating links face in thesame direction in the non-directional stent. Because the proximal anddistal ends of the stent are generally mirror image configurations or arotated mirror image of the opposite end of the stent, and theconfiguration of peaks and valleys of the rings is reversed at one ormore points along the length of the stent, the non-directional stent maybe mounted onto a stent delivery system in either direction.

Other features and advantages of the present invention will become moreapparent from the following detailed description of the invention, whentaken in conjunction with the accompanying exemplary drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is herein described, by way of example only, withreference to the accompanying drawings, wherein:

FIG. 1 is a plan view of a portion of a flattened stent of oneembodiment of the invention which illustrates a pattern of rings andlinks.

FIG. 2A is a plan view of a portion of the stent of FIG. 1 forming aradially compressed cylindrical configuration.

FIG. 2B is a perspective view of a portion of the stent of FIG. 2A.

FIG. 3A is a plan view of a portion of the stent of FIG. 1 in aflattened configuration and illustrating the rings and links in anexpanded configuration.

FIG. 3B is a perspective view of a portion of the stent of FIG. 1 in acylindrical configuration and illustrating the rings and links in anexpanded configuration.

FIG. 4 is an enlarged plan view of a portion of the stent of FIG. 1.

FIG. 5 is an enlarged plan view of a portion of an embodiment of a stentincluding straight links in an expanded configuration.

FIG. 6 is an enlarged cutaway perspective view of a portion of anembodiment of a stent having struts with varying radial thickness.

FIG. 7 is an enlarged plan view of a portion of the stent of FIG. 1.

FIG. 8A is a plan view of a portion of one embodiment of anon-directional stent in a flattened configuration.

FIG. 8B is a perspective view of a portion of the stent of FIG. 8A in acylindrical configuration.

FIG. 9A is a plan view of a portion of the stent of FIG. 8A in aflattened compressed configuration.

FIG. 9B is a perspective view of a portion of the stent of FIG. 9Aforming a radially compressed cylindrical configuration.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to the drawings, which are provided for purposes ofillustration and by way of example but not limitation, the presentinvention is illustrated in FIGS. 1-9B.

Turning now to FIG. 1, an exemplary stent 30 of the present invention isshown in a flattened condition so that the pattern can be clearlyviewed, even though the stent is in a cylindrical form in use, such asshown in FIGS. 2A-B. The stent is typically formed from a tubularmember, however it can be formed from a flat sheet such as shown in FIG.1 and rolled into a cylindrical configuration.

As shown in FIGS. 1-3B, stent 30 is made up of a plurality ofcylindrical rings 40 which extend circumferentially around the stent. Itis to be recognized that there may be fewer or more cylindrical ringsthan is shown in the illustrated drawings. The rings are aligned along acommon longitudinal axis and interconnected by links 54 to form thestent. The links 54 can be generally straight members (See FIG. 5) orcan include one or more curves or turns as shown in the figures.Moreover, links with undulation can be configured at all locations orany selected locations along the stent. The stent has a deliverydiameter 42 (FIG. 2A), and expands to an implanted diameter 44 (FIGS. 3Aand 3B). The stent has a proximal end 46 and a distal end 48. Typically,since the stent is contemplated to be laser cut from a tube, there areno discreet parts.

Referring specifically to FIG. 2B, each cylindrical ring includes acylindrical outer wall surface 52 which defines the outermost surface ofthe stent and a cylindrical inner wall surface 53 which defines theinnermost surface of the stent. The links 54 connect one cylindricalring 40 to an adjacent cylindrical ring 40. To prevent links 54 fromcompromising the longitudinal flexibility of the stent, a curved portion56 is incorporated into link 54. This curved portion 56 is connected toone or more substantially straight portions 58 wherein the straightportions 58 are substantially perpendicular to the longitudinal axis ofthe stent. Thus, as the stent is being delivered through a tortuousvessel, such as a coronary artery, the curved portions 56 and straightportions 58 of the undulating links will permit the stent to flex in thelongitudinal direction which substantially enhances delivery of thestent to the target site. The number of bends and straight portions in alink can be increased or decreased from that shown to achieve differentflexibility constructions. In one embodiment (not shown), it iscontemplated that the links can comprise a plurality of curved portionsand straight portions 58. With the straight portions being substantiallyperpendicular to the stent longitudinal axis, the link 54 acts much likea hinge at the curved portion 56 to provide flexibility in both crimpedand expanded states. The number of links 54 can be adjusted to vary thelongitudinal flexibility in the crimped and expanded states of a stent.

The stent 30 further can be described as having rings including aplurality of alternative peaks and valleys. The peaks and valleys canhave similar or different sizes. In one embodiment, the rings caninclude one or more open W or butterfly patterns of struts to whichlinks between adjacent rings are connected. Accordingly, the rings caninclude a plurality of short peaks 60, tall peaks 61, intermediate peaks62, shallow valleys 90, deep valleys 91, and intermediate valleys 92.The peaks and valleys are formed from various length struts and apices112. In one embodiment, the struts include short struts 66, long struts67, and intermediate struts 68. The lengths of these struts can bevaried to achieve a desired expansion diameter. As shown, each open W orbutterfly pattern is defined by one short peak 60, two short struts 66,one long strut 67 and one intermediate strut 68. The struts can beeither curved or straight depending upon a particular application. Also,as shown, each peak has a height, the tall peaks being taller than theintermediate peaks, and the intermediate peaks being taller than theshort peaks. Additionally, each valley has a depth, the deep valleysbeing deeper than the intermediate valleys, and the intermediate valleysbeing deeper than the shallow valleys. In other embodiments, a greaterrange in the types of heights of peaks and/or a greater range in thetypes of depths of valleys may be included.

Additionally, in one aspect, the stent 30 can further include one ormore Y patterns of struts. With reference to FIG. 2B, the Y pattern isdefined by one intermediate valley 92, one long strut 67, and oneintermediate strut 68.

It is also contemplated that a stent of the present invention canfurther include at least one additional peak (not shown) having adifferent height than the short peak, the tall peak, and theintermediate peak. Also, the stent can further include at least oneadditional valley (not shown) having a different depth than the shallowvalley, the intermediate valley, and the deep valley. For example, oneembodiment may have four different height peaks and four different depthvalleys. Moreover, the number of peaks and valleys can vary in numberfor each ring depending upon the application. Thus, for example, if thestent is to be implanted in a coronary artery, a lesser number of peaksand valleys are required than if the stent is implanted in a peripheralartery, which has a larger diameter than a coronary artery. Moreover,the number of peaks and valleys can be adjusted to vary the expansiondiameter. Furthermore, the order or juxta-positioning of various sizedpeaks and valleys can be varied within a ring or from one ring toanother, and the various peaks and valleys of adjacent rings can bealigned or offset from each other. It is to be understood that thedefinition of an open W pattern should not be limited but generallyshould imply the presence of a plurality of apexes including both one ormore peaks and valleys of different heights and depths.

In one particular embodiment, illustrated as example in the peaks 60, 61and 62 of each ring 40 are oriented towards the proximal end 46, and thevalleys 90, 91 and 92 of each ring 40 are oriented towards the distalend 48. These rings can be positioned in phase relatively to oneanother, meaning that the peaks of one ring are separated from the peaksof the adjacent ring by one ring width plus the spacing between therings. Likewise, the valleys of one ring are separated from the valleysof the adjacent ring by one ring width plus the spacing between therings.

As stated, it may be desirable under certain circumstances to positionthe peaks so that they are out of phase (not shown), that is, the apexesof the peaks of one ring are circumferentially offset from the apexes ofthe peaks of an adjacent ring. Positioning the peaks, valleys, and linksin this manner, provides a stent having desirable expansioncapabilities, high radial strength, a high degree of flexibility, andsufficient wall coverage to support a vessel.

As can be seen, for example, in FIGS. 1-2B, curved portion 56, straightportions 58 have been designed such that when crimped, intermediate peak62 would nest in the space just distal to the curved portion 56 andstraight portions 58. This nesting allows the stent 30 to be tightlycrimped onto a delivery system to achieve a low crimped OD.

Referring to FIGS. 2A-2B, the crimping or compressing process,circumferentially moves the undulating link 54 along with its curvedportion 56 closer to the intermediate peak 62. Although the variousstent struts, curved portions, links, and peaks and valleys may contacteach other when the stent is crimped or compressed, it may be desirableto avoid the overlapping of struts 66, 67, 68, apexes 112, and links 54.

Referring now to FIG. 4, in one embodiment, an arm 76 of the link 54 isattached to the apex 112 of a short peak 60. The length of the arm mayvary in different embodiments. The other end 78 of the link 54 isattached to the apex 112 of an intermediate valley 92. Notably, in thisembodiment, combined height “H” of the short peak 60 and the arm 76 islonger than the length of the intermediate peak 62 when the stent is inboth the compressed and expanded configurations. This allows the stentto be tightly compressed onto a catheter or other stent delivery device,and such structure can be employed to avoid overlapping between theundulating link 54 and the intermediate peak 62. In addition, thecircumferential positioning of the intermediate peak 62 and tall peaks61 can be varied to avoid the intermediate peak 62 and tall peak 61 fromtouching arm 78 of link 54.

Due to the intricate patterns as disclosed in FIGS. 1-4, the rate ofexpansion of the various portions of the stent can vary. Accordingly,one aspect of the invention provides for different radii of curvature atvarious apexes 112 so that the stent will expand evenly and uniformly.Referring more specifically now to FIG. 4, first radius 71 whichcorresponds with tall peak 61 may have a smaller radius of curvaturethan does second radius 72 which corresponds with intermediate peak 62.Generally, the longer the struts associated with a peak, the more easilythat portion of the stent will expand, so that a smaller radius isassociated with peaks having two long struts 67. Likewise, for peaks,such as short peak 60, which has struts 66 that are shorter than thestruts 67 of tall peak 61, the apex 112 may have a greater radius 73 ofcurvature which will expand more easily in order to compensate for thestiffer bending moments created by the shorter struts 66. In yet otherembodiments, the radii of curvature of the various peaks and variousvalleys may be adjusted so that the different types of peaks and valleysexpand at different tensions rather than expanding uniformly. Inaddition, the circumferential positioning of the intermediate peak 62and tall peaks 61 can be varied to achieve uniform expansion.

The radii 75 of the shallow valleys 90 may also be varied to provideuniform stent expansion. Since a shallow valley formed by anintermediate strut 68 and a short strut 66 can have a tendency to expandmore slowly as the stent is expanded compared to a shallow valley formedby a long strut 67 and a short strut 66, a greater radius of a curvaturemay be incorporated into the shallow valley having the intermediatestrut 68. Thus, third radius 75 of a first shallow valley 90A may begreater than the fourth radius 75 of a second adjacent shallow valley90B. By varying the radii of curvature in the shallow valleys, the stentmay expand more evenly and compensate for the varying rates of expansionof adjacent portions in a cylindrical ring.

Typical stents known in the art undergo a lot of strain as they go froma compressed configuration to an expanded configuration. The strainproduced by the expansion of a stent may cause the links to beangulated, resulting in a twisted stent. With reference to FIG. 5, theopen W butterfly pattern 94 is shown including two shallow valleys 90connected with each other by a short peak 60. The butterfly pattern 94is designed to reduce the strain exerted on the peaks 60, 61, 62,valleys 90, 91, 92, struts 66, 67, 68, and links 54 during expansion ofthe stent 30. Moreover, the butterfly pattern 94 design facilitatesachieving better crimping profiles since the short crest and long crestare positioned further away from the linear link, so during crimping thelong crest and short crest have a longer distance to travel beforehitting the linear link. It is especially beneficial when the stent iscoated with a drug because it prevents or at least minimizes apossibility of coating damage. Moreover, the butterfly W crest increasesthe stent flexibility since both valleys 90 are two separate componentswhich can move to accommodate any bending when the crimped stent tracksthrough tortuousity.

As previously stated, it is also a design feature that more or fewerlinks 54 including curved portions be positioned between adjacentcylindrical rings 40. As shown in FIG. 5, straight links 84 in additionto undulating links 54 may be included to connect adjacent cylindricalrings. The straight links can be employed to provide stability andassist in stent length change, as an adjunct to the undulating links.

Further, the straight links may be employed in various alternativeapproaches to provide more rigidity in a localized area, such as at thestent ends. For example, it may be desirable to incorporate morestraight links between the cylindrical rings at the stent ends 46, 48(FIG. 2B) than in the interposed rings 40A, 40B, 40C (FIG. 1) of thestent. In fact, in one contemplated embodiment, all links can assume asubstantially straight configuration.

In another aspect of the invention, as shown in FIG. 6, the stent 30 isformed so that the various elements of the cylindrical rings 40,including the long struts 67, short struts 66, intermediate struts 68,various peaks 60, 61, 62, various valleys 90, 91, 92, and the undulatinglinks 54, all can be formed so that each has a variable thickness alongthe stent length. For example, the undulating link 54 may be thicker atthe arm 76 portion than at the extension 78 portion of the link. Suchstructure can reduce deployment pressure while maintaining radialstrength. Further, short struts 66, long struts 67, and intermediatestruts 68 may vary in thickness (radial thickness) along their length inorder to create variable flexibility in the rings. Moreover, in onecontemplated approach short peak 60 has short struts 66 that can haveradial thick portion 80 in the middle of the struts and radial thinportion 82 near the ends of the struts. As another example (not shown),the ring 40E at the proximal end 46 and/or ring 40 at the distal end 48of the stent may be thicker radially than the other cylindrical rings 40of the stent. It is also to be recognized that the proximal end ring 40Ecan have a unique configuration, one that is different from theremaining rings of the stent 30.

Turning now to FIG. 7, in one contemplated embodiment, at least onecylindrical ring 40 includes a repeating pattern of peaks and valleys.That is, for example, each pattern segment 88 includes in sequence ashort peak 60, a shallow valley 90B, a tall peak 61A, a deep valley 91,a tall peak 61B, an intermediate valley 92, an intermediate peak 62, anda shallow valley 90A. The pattern segment may repeat itself as manytimes as necessary to provide a cylindrical ring of a desired expansiondiameter. Also, adjacent cylindrical rings can be connected by oneundulating link 54 per pattern segment. For example, an undulating linkmay connect the short peak 60 of one cylindrical ring to theintermediate valley 92 of an adjacent cylindrical ring. Further, theremay be more than one undulating link 54 or straight link 84 (FIG. 5) perpattern segment. In other contemplated embodiments, the links 54, 84 mayconnect any of the various types of peaks 60, 61, 62 and valleys 90, 91,92 to any other or same type of peak or valley. Adjacent cylindricalrings can have the same repeating pattern or may have differentrepeating patterns from each other.

Referring back now to FIG. 1, in one embodiment, the stent of thepresent invention includes a repeating pattern segment including fourpeaks and four valleys, and the short peak 60 of a first ring 40A islinked to and longitudinally aligned with the intermediate valley 92 ofan adjacent second ring 40B. The short peak 60 of the second ring 40B islinked to and longitudinally aligned with the intermediate valley 92 ofan adjacent third ring 40C. In other words, the pattern of the secondring 40B is rotated from the pattern of the first ring 40A, and thepattern of the third ring 40C is further rotated from the pattern of thesecond ring 40B. This rotational pattern results in the short peaksbeing longitudinally aligned every third cylindrical ring. Such a threering longitudinal design may then be repeated as desired to addadditional length to a stent. In at least one embodiment, the mostproximal end 46A or most distal end 46B of the stent 30 may have a row40E of undulations having all the same length struts 66, or 67, or 68.

Referring now to FIGS. 8A-9B, yet another aspect of the stent 30 isembodied in a non-directional stent. Notably, the non-directional stentmay be mounted on a delivery device with either the proximal or distalend of the stent oriented towards the distal end of the delivery devicewith equal effectiveness. Thus, the non-directional stent may be mountedonto a stent delivery system (not shown), for example a ballooncatheter, without it being positioned in a preferred proximal-distalorientation. FIGS. 8A-8B show representative features of a portion ofthe non-directional stent in an as-manufactured (flat and cylindrical)configuration, and FIGS. 9A-9B show representative features of a portionof the non-directional stent in a compressed configuration (flat andcylindrical).

In one embodiment of the non-directional stent, all of apexes 112 of thepeaks 60, 61, 62 on the most proximal end 46 cylindrical ring 40 of thestent 30 point distally and, all of apexes 112 of the peaks 60, 61, 62on the most distal end 48 cylindrical ring 40 point proximally.Similarly, all of the valleys 90, 91, 92 of the most distal end 48 ring40 face proximally, and all of the valleys of the most proximal end 46ring 40 face distally. Stated another way, all of the peaks on theproximal end 46 ring 40 point towards all of the peaks on the distal end48 ring 40. Additionally, all of the valleys on the proximal end 46 ring40 point towards all of the valleys on the distal end 48 ring 40.

In a further aspect, along the entire length of the stent, there may beapproximately equal numbers of peaks 60, 61, 62 having apexes 112 thatpoint towards the proximal end 46 of the stent 30 and peaks havingapexes that point towards the distal end 48 of the stent. There may alsobe along the entire length of the stent approximately equal numbers ofvalleys 90, 91, 92 having apexes 112 that point towards the proximal end46 of the stent 30 and valleys having apexes that point towards thedistal end 48 of the stent.

In still another aspect (not shown), it is contemplated that at leastsome of the intervening rings 40 that are located between the proximalend 46 and the distal end 48 may include peaks 60, 61, 62 having apexes112 that point proximally, and some of the other rings may include peakshaving apexes that point distally. Similarly, at least some of theintervening rings 40 that are located between the proximal end 46 andthe distal end 48 may include valleys 90, 91, 92 having apexes 112 thatpoint proximally, and some of the other rings may include valleys havingapexes that point distally.

Moreover, in each of the rings 40 of the stent 30 there may beapproximately equal number of peaks 60, 61, 62 having apexes 112 thatpoint towards the proximal end 46 of the stent and peaks having apexesthat point towards the distal end 48 of the stent. There may also be ineach of the rings of the stent approximately equal number of valleys 90,91, 92 having apexes that point towards the proximal end of the stentand valleys having apexes that point towards the distal end of thestent.

Furthermore, not all of the apexes 112 of the peaks 60, 61, 62 on onering 40 need to be aligned in the same direction. For example, some ofapexes 112 of the peaks 60, 61, 62 on the ring 40 may point distally 48,and some of the apexes of the peaks on the ring 40 may point proximally46. Also, some of apexes 112 of the valleys 90, 91, 92 on the ring 40may point distally 48, and some of the apexes of the valleys on the ring40 may point proximally 46. Additionally, the rings may be rotationallyoffset from each other or configured to be in-phase.

As illustrated in FIG. 8A, the non-directional stent includes at leasttwo of the butterfly patterns oriented in opposite longitudinaldirections from each other. Moreover, in certain approaches, it may bedesirable to configure the stent so that the oppositely orientedbutterfly pattern may be on the same ring or on different rings. Forexample, butterfly 94C has an opposite longitudinal orientation frombutterfly 94D.

In at least one additional embodiment, not all of the curved portions 56of the undulating links 54 face in the same orientation in thenon-directional stent. For example, as shown in FIGS. 8A-9B, curvedportion 56A of undulating link 54A faces in an opposite circumferentialdirection from curved portion 56B of undulating link 54B.

Furthermore, it is also contemplated that a non-directional stent of thepresent invention can include both the oppositely oriented butterflypatterns of FIG. 8A as well as undulating links facing in oppositecircumferential directions as depicted in FIG. 8B. Moreover, suchfeatures can be incorporated into directional stents where desired.

Additionally, in the non-directional stent (See FIGS. 8-9B), theintermediate struts 68 can be configured to remain adjacent to thecurved portions 56 of the undulating links 54. Furthermore, the arm 76of the undulating link 54 is typically connected to a short peak 60 inthe various embodiments of the non-directional stent.

The stent 30 of the present invention can be made in many ways. Onemethod of making the stent is to cut a thin-walled tubular member, suchas a stainless steel tubing to remove portions of the tubing in thedesired pattern for the stent, leaving relatively untouched the portionsof the metallic tubing which are to form the stent. The stent also canbe made from other metal alloys such as tantalum, nickel-titanium,cobalt-chromium, titanium, shape memory and superelastic alloys, and thenobel metals such as gold or platinum. In accordance with the invention,it is preferred to cut the tubing in the desired pattern by means of amachine-controlled laser as is well known in the art.

Other methods of forming the stent of the present invention can be used,such as using different types of lasers, chemical etching, electricdischarge machining, laser cutting a flat sheet and rolling it into acylinder, and the like, all of which are well known in the art at thistime.

The stent of the present invention also can be made from metal alloysother than stainless steel, such as shape memory alloys. Shape memoryalloys are well known and include, but are not limited to,nickel-titanium and nickel-titanium-vanadium. Any of the shape memoryalloys can be formed into a tube and laser cut in order to form thepattern of the stent of the present invention. As is well known, theshape memory alloys of the stent of the present invention can includethe type having superelastic or thermoelastic martensitic transformationor display stress-induced martensite. These types of alloys are wellknown in the art and need not be further described here.

The present invention stent is also ideally suited for drug delivery(i.e., delivery of a therapeutic agent) since it has a uniform surfacearea which ensures uniform distribution of drugs. Typically, a polymercontaining the drug is coated onto the stent of the type disclosed inU.S. Pat. Nos. 6,824,559 and 6,783,793 which are incorporated herein byreference.

It is contemplated that the stent 30 of the present invention can bemounted on a stent delivery device or system, for example, a ballooncatheter (not shown) similar to those known in the prior art. The stentdelivery device includes a distal end for mounting of a stent thereon,and a proximal end configured to remain external to a patient's bloodvessel. An example of a stent delivery system is disclosed in U.S. Pat.No. 6,629,994 entitled “INTRAVASCULAR STENT” filed Jun. 11, 2001, theentirety of which is incorporated herein by reference. The presentinvention, however, is not intended to be limited to delivery using thedisclosed stent delivery systems but may be used with other stentdelivery systems known in the art. The stent may be tightly compressedor crimped on the balloon portion of the catheter and remains tightlycrimped on the balloon during delivery through the patient's vascularsystem. When the balloon is inflated, the stent expands radiallyoutwardly into contact with the body lumen, for example, a coronaryartery. When the balloon portion of the catheter is deflated, thecatheter system is withdrawn from the patient, and the stent remainsimplanted in the artery.

Similarly, if the stent of the present invention is made from aself-expanding metal alloy, such as nickel-titanium or the like, thestent may be compressed onto a catheter, and a sheath (not shown) isplaced over the stent to hold it in place until the stent is ready to beimplanted in the patient. Such sheaths are well known in the art. Oncethe stent has been positioned at the intended location, the sheath isretracted and the stent self-expands into contact with the wall of theartery. Catheters for delivering self-expanding stents are well known inthe art.

It is to be recognized that the invention may be embodied in other formswithout departing from the spirit and essential characteristics thereof.The embodiments described therefore are to be considered in all respectsas illustrative and not restrictive. Although the present invention hasbeen described in terms of certain preferred embodiments, otherembodiments that are apparent to those of ordinary skill in the art arealso within the scope of the invention. Accordingly, the scope of theinvention is intended to be defined only by reference to the appendedclaims.

What is claimed:
 1. A flexible intravascular stent for use in a bodylumen, comprising: a plurality of cylindrical rings aligned along acommon longitudinal axis; and a plurality of links connecting adjacentcylindrical rings, two or more of the plurality of links being anundulating link, each undulating link having a curved portion extendingtransverse to the common longitudinal axis and an arm being straight andparallel to the common longitudinal axis; wherein each cylindrical ringincludes an open W-pattern, the open W-pattern being connected to nomore than one adjacent ring, each of the cylindrical rings having aplurality of first peaks, second peaks, and third peaks, each of thefirst, second and third peaks having a height and an apex, the firstpeaks being taller than the second peaks, and the second peaks beingtaller than the third peaks along with a plurality of first valleys,second valleys, and third valleys, each of the first, second and thirdvalleys having a depth and an apex, the first valleys being deeper thanthe second valleys, and the second valleys being deeper than the thirdvalleys, each third peak of at least one of the cylindrical rings beingconnected to an adjacent cylindrical ring by one of the undulating linksand the open W-pattern is formed between one of the first peaks and oneof the second peaks.
 2. The stent of claim 1, wherein each undulatinglink further includes at least one substantially straight portionconnected to the curved portion, the at least one substantially straightportion being substantially perpendicular to the common longitudinalaxis.
 3. The stent of claim 2, wherein the at least one substantiallystraight portion of each undulating link is perpendicular to the commonlongitudinal axis.
 4. The stent of claim 1, wherein the apexes of thefirst peaks have a first radius, and the apexes of the second peaks havea second radius, the second radius being different than the firstradius.
 5. The stent of claim 1, wherein each cylindrical ring includesa plurality of a first strut, a second strut, and a third strut, thefirst struts being longer than the second struts, and the second strutsbeing longer than the third struts.
 6. The stent of claim 1, wherein thestent has a proximal end and a distal end and defines a firstlongitudinal orientation of the apexes of the first, second and thirdpeaks and the apexes of the first, second and third valleys at theproximal end which is generally reversed from a second longitudinalorientation of the apexes of the first, second and third peaks and theapexes of the first, second and third valleys at the distal end.
 7. Thestent of claim 1, wherein the stent has a proximal end and a distal endand the apex of at least one third peak of one of the cylindrical ringsis oriented towards the proximal end of the stent, and the apex of atleast one other third peak on another of the cylindrical rings isoriented towards the distal end of the stent.
 8. The stent of claim 1,wherein orientations of at least some of the peaks and some of thevalleys are longitudinally reversed along a length of the stent, whereinthe stent may be effectively mounted onto a stent delivery system in atleast two different orientations.
 9. The stent of claim 1, wherein aplurality of struts define the rings and each link, at least a portionof one strut having a variable thickness.
 10. The stent of claim 1,wherein a plurality of struts define the rings and each link, at least aportion of one strut having a variable width.
 11. The stent of claim 1,wherein the open W-pattern includes two short struts connected togetherto form one of the third peaks having a radius, a first long strutconnected to one end of one of the short struts to form one of the firstvalleys having a radius and a second long strut connected to one end ofthe other short strut to form one of the second valleys having a radius.12. The stent of claim 1, wherein each of the first peaks has a smallerradius of curvature than each of the second peaks and each of the secondpeaks has a smaller radius of curvature than each of the third peaks.13. A flexible intravascular stent for use in a body lumen, comprising:a plurality of cylindrical rings aligned along a common longitudinalaxis; and a plurality of links connecting adjacent cylindrical rings;wherein each cylindrical ring includes an open W-pattern, the openW-pattern being connected to no more than one adjacent ring, each of thecylindrical rings having a plurality of first peaks, second peaks, andthird peaks, each of the first, second and third peaks having a heightand an apex, the first peaks being taller than the second peaks, and thesecond peaks being taller than the third peaks along with a plurality offirst valleys, second valleys, and third valleys, each of the first,second and third valleys having a depth and an apex, the first valleysbeing deeper than the second valleys, and the second valleys beingdeeper than the third valleys, each third peak of at least one of thecylindrical rings being connected to an adjacent cylindrical ring by oneof the links and the open W-pattern is formed between one of the firstpeaks and one of the second peaks and each cylindrical ring includes aplurality of a first strut, a second strut, and a third strut, the firststruts being longer than the second struts, and the second struts beinglonger than the third struts and the open W-pattern is defined by a pairof third struts, one first strut and one second strut.
 14. A flexibleintravascular stent for use in a body lumen, comprising: a plurality ofcylindrical rings aligned along a common longitudinal axis; and aplurality of links connecting adjacent cylindrical rings; wherein eachcylindrical ring includes an open W-pattern, the open W-pattern beingconnected to no more than one adjacent ring, each of the cylindricalrings having a plurality of first peaks, second peaks, and third peaks,each of the first, second and third peaks having a height and an apex,the first peaks being taller than the second peaks, and the second peaksbeing taller than the third peaks along with a plurality of firstvalleys, second valleys, and third valleys, each of the first, secondand third valleys having a depth and an apex, the first valleys beingdeeper than the second valleys, and the second valleys being deeper thanthe third valleys, each third peak of at least one of the cylindricalrings being connected to an adjacent cylindrical ring by one of thelinks and the open W-pattern is formed between one of the first peaksand one of the second peaks and each cylindrical ring includes aplurality of a first strut, a second strut, and a third strut, the firststruts being longer than the second struts, and the second struts beinglonger than the third struts and at least one of the second valleysincludes one of the second struts connected with another of the secondstruts by one of the apexes.
 15. A flexible intravascular stent for usein a body lumen, comprising: a plurality of cylindrical rings alignedalong a common longitudinal axis; and a plurality of links connectingadjacent cylindrical rings; wherein each cylindrical ring includes anopen W-pattern, the open W-pattern being connected to no more than oneadjacent ring, each of the cylindrical rings having a plurality of firstpeaks, second peaks, and third peaks, each of the first, second andthird peaks having a height and an apex, the first peaks being tallerthan the second peaks, and the second peaks being taller than the thirdpeaks along with a plurality of first valleys, second valleys, and thirdvalleys, each of the first, second and third valleys having a depth andan apex, the first valleys being deeper than the second valleys, and thesecond valleys being deeper than the third valleys, each third peak ofat least one of the cylindrical rings being connected to an adjacentcylindrical ring by one of the links and the open W-pattern is formedbetween one of the first peaks and one of the second peaks and eachcylindrical ring includes a plurality of a first strut, a second strut,and a third strut, the first struts being longer than the second struts,and the second struts being longer than the third struts and at leastone of the second struts is of dissimilar length than at least one otherof the second struts.
 16. A flexible intravascular stent for use in abody lumen, comprising: a plurality of cylindrical rings aligned along acommon longitudinal axis; and a plurality of links connecting adjacentcylindrical rings; wherein each cylindrical ring includes an openW-pattern, the open W-pattern being connected to no more than oneadjacent ring, each of the cylindrical rings having a plurality of firstpeaks, second peaks, and third peaks, each of the first, second andthird peaks having a height and an apex, the first peaks being tallerthan the second peaks, and the second peaks being taller than the thirdpeaks along with a plurality of first valleys, second valleys, and thirdvalleys, each of the first, second and third valleys having a depth andan apex, the first valleys being deeper than the second valleys, and thesecond valleys being deeper than the third valleys, each third peak ofat least one of the cylindrical rings being connected to an adjacentcylindrical ring by one of the links and the open W-pattern is formedbetween one of the first peaks and one of the second peaks and eachcylindrical ring includes a plurality of a first strut, a second strut,and a third strut, the first struts being longer than the second struts,and the second struts being longer than the third struts and each of thesecond peaks includes one of the second struts connected with another ofthe second struts at the apex which defines that second peak.